-1 


; TS 1109 


.H77 


| Copy 1 



DEPARTMENT OF COMMERCE 



Technologic Papers 



OF THE 



Bureau of Standards 

S. W. STRATTON, Direotor 



No. 187 

a study of test methods for the purpose 

of developing standard specifications 

for paper bags for cement and lime 



BY 

PAUL L. HOUSTON, Associate Physicist 
Bureau, of Standards 



MARCH 21, 1921 




-7- Is 1 6 



PRICE; 5 CENTS 



Sold only by the Superintendent o( Documents, Government Printing Office 
Washington. D. C. 

WASHINGTON . 

GOVERNMENTi'PRINTING OFFICB 

1921 



DEPARTMENT OF COMMERCE 



Technologic Papers 



OF THE 



Bureau of Standards 

S. W. STRATTON, Director 



No. 187 

A STUDY OF TEST METHODS FOR THE PURPOSE 

OF DEVELOPING STANDARD SPECIFICATIONS 

FOR PAPER BAGS FOR CEMENT AND LIME 



BY 

PAUL L. HOUSTON, Associate Physicist 
Bureau of Standards 



MARCH 21, 1921 




PRICE. 5 CENTS 

Sold only by the Superintendent of Documents, Government Printing Office 
Washington, D. C. 

WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1921 



fl 



1^ 






II n II llllWHIHilil 1IHMIJ ii 

LIBRARY OF CONGRESS 
pfOEIVEb 

APR 851921 

DoeyMENTs c aiON 



II-IU3C 



A STUDY OF TEST METHODS FOR THE PURPOSE OF 
DEVELOPING STANDARD SPECIFICATIONS FOR 
PAPER BAGS FOR CEMENT AND LIME 

By Paul L. Houston 



ABSTRACT 

This technologic paper contains information relating to the methods of testing 
and the apparatus employed in determining the quality of paper bags for lime and 
cement. A brief description is given of the ordinary tests performed on paper, such 
as weight in pounds of the standard size ream 2 5 X40— 500, bursting strength in points, 
tensile strength in kilograms, stretch in centimeters, folding endurance in number of 
double folds, percentage of fiber composition, percentage of ash, and percentage of 
rosin sizing. A special test is developed for giving numerically the stresses and 
strains that the paper of these bags undergo in service. This test is called a resiliency 
or endurance test. A service test is also given to determine the breaking strength 
of the paper when the bags are filled and dropped. A comparison is made of the results 
of this test with the results of the above resiliency test. Another service test is devel- 
oped for determinining the strength of the adhesives used in these bags. The results of 
all these tests are tabulated, and from these data the very best quality bags are chosen. 
In the conclusions, special consideration is given this choice of best bags in deter- 
mining the characteristics of a good quality bag, and specifications are drawn up 
accordingly. 



CONTENTS 

Page 

I. Introduction 3 

1. Purpose of tests 3 

2 . Discussion of materials and apparatus used 4 

3. Scope of the tests and methods employed 6 

II. Experimental work 7 

1. Physical and chemical tests 7 

2. Tables of results 8 

3. Diagrams illustrating results n 

III. Conclusions 18 

IV. Specification 18 

I. INTRODUCTION 

1. PURPOSE OF TESTS 

The purpose of these tests is to aid the paper-bag manuf acturers 
to meet the requirements of the lime and cement manufacturers 
in obtaining a suitable paper bag in which to ship their product. 
For a number of years the paper-bag manufacturers have attempted 
to manufacture such an article to substitute for the cotton bag 

3 



4 Technologic Papers of the Bureau of Standards 

that had hitherto been used with great expense to the lime and 
cement industries because of the high price of cotton. The 
success of the paper-bag industry in this undertaking has been 
varied. A few of the consumers have given favorable reports 
on the use of their product, while others have claimed the bags 
fail in service. A number of consumers claim the glue gives way 
easily if the bags are held in storage any length of time. Since 
the bag manufacturers have been unable to derive any decided 
benefit from the above reports of the consumers, the present 
study was undertaken in order to develop specifications for these 
paper bags. 

2. DISCUSSION OF MATERIALS AND APPARATUS USED 

The materials used for this study were representative samples 
of paper bags obtained from a number of the leading bag manu- 
facturers. The bags were given the following identification 
numbers: 14373, H374. 14375. 14376, H377. H378, H379, 
14380, and 1 438 1. The apparatus used was the Mullen paper 
tester, the paper scales, the 200 kg tensile-strength instrument, 
the 50 kg tensile-strength instrument, the folding endurance 
machine, microscope, glass slides, test tubes, extraction flasks, 
siphon cups, evaporating dishes and crucibles, all of which are used 
for ordinary physical and chemical tests. Descriptions and photo- 
graphs of these instruments and apparatus may be obtained from 
circular of the Bureau of Standards No. 107, with the exception of 
the large 200 kg tensile-strength machine. The description and 
photograph of the tensile-strength apparatus in the above circular 
apply to the small 50 kg instrument. However, the 200 kg and 
the 50 kg instruments are practically identical in construction, the 
200 kg machine being used for any material breaking at or under 
a load of 200 kg, the 50 kg machine for material breaking at or 
under a 50 kg load. In addition to the above paper-testing instru- 
ments a wooden platform with trapdoor and an ordinary foundry 
jolter were used for service tests. The wooden platform was built 
3 feet high and allowed a bag filled with sand to be dropped 
through its trapdoor onto a solid wooden stand. The jolter con- 
sisted of a solid iron plate 3 inches thick which could be raised 
and lowered in rapid succession by means of air pressure. This 
machine, of course, was constructed with the necessary intake and 
outlet valves, air chamber, and piston to allow for the continuous 
jolting movement of the plate. For the purpose of developing a 
laboratory test that would give numerically the resiliency of bag 



Testing Paper Bags for Cement and Lime 5 

paper or the stress and strain that the paper of a bag undergoes 
in service and by which the results of the above service tests 
could be checked, the large 200 kg tensile-strength machine was 
adopted with the following additional attachments : A brass cylinder 
was constructed and fastened to the upright standard in such a 
way that it would revolve. The revolution of this cylinder was 
controlled by a small wire over a pulley from the weighted pendu- 
lum so that, as the pendulum moved from its vertical position 
due to the increasing loads, the cylinder revolved accordingly. 
This cylinder held a paper chart, and a glass recording pen was 
used to record both load and stretch. The pen was controlled 
by a small wire extending from the lower-jawed arm over a pulley 
in such a way that, as the lower jaw descended and the paper 
stretched under the load, the pen ascended and described a curve 
which registered stretch. It can thus be seen that the revolution 
of the cylinder caused the registering of load on the chart, while 
the ascension of the pen caused the registering of stretch. The 
result was a curve on the chart giving both the increasing load and 
increasing stretch until the paper broke. In order to read this 
curve it was necessary to draw up the chart so that load and stretch 
could be read at a glance. The method used was as follows: 
An ordinary blank piece of writing paper was used for this purpose 
and placed in position on the cylinder. A point on the paper 
was chosen as the zero point for load and stretch. Then the 
zero line for stretch was found by using a piece of steel between 
the jaws and by applying the various loads. Steel was used for 
this purpose because the chart was to be drawn up for a 70 kg 
load as a maximum, and steel would not stretch at this load. 
By this method the zero line for stretch was drawn with the record- 
ing pen from the zero point, and each kilogram load as indicated 
by the scale was pointed off as the load increased. At each kilo- 
gram point a line was drawn parallel to the base or zero line for 
load. This base line was found by operating the machine with 
nothing between the jaws and was drawn with the recording pen 
from the zero point. Each centimeter that the lower jaw de- 
scended from its starting position or zero point represented stretch 
and was pointed off accordingly. At the different centimeter 
points lines were drawn parallel to the zero line for stretch. In 
this way the chart was plotted to give accurately the stretch at 
different loads foi any paper breaking under a 70 kg load. 



6 Technologic Papers of the Bureau of Standards 

3. SCOPE OF THE TESTS AND METHODS EMPLOYED 

The object of these tests was, first, to discover all the physical 
and chemical properties of the paper of the bags; second, to 
check these results with the results of service tests on the bags 
themselves; third, to choose by the process of elimination the 
best bags of the series ; and fourth, to develop specifications from 
this choice of best bags. For the ordinary physical and chemical 
tests the methods employed have been fully described in Circular 
of the Bureau of Standards No. 107, with the exception of the 
tensile strength and stretch tests. For these tests, the 200 kg 
instrument was used, and test samples were cut 1% cm wide and 
long enough to allow 20 cm between jaws. In addition to the 
above tests a wet tensile test was conducted in the same manner 
as the dry tensile test described in the above Circular, with the 
following exceptions : The weight was removed from the pendulum 
of the 50 kg tensile-strength instrument, the machine was calibrated 
to find the corrections for the scale readings, and the paper was 
immersed for 10 minutes in water before testing. In both service 
tests bags were filled with 94 pounds of sand and then dropped or 
jolted until they broke open. In the jolter test the bags were 
jolted 1 inch high and 170 times per minute. An average of five 
tests was taken in each of these service tests to determine the 
strength of the bag. The method used for obtaining the resiliency 
of paper on the tensile-strength machine with its recording device 
was the following: In order to obtain curves or loops (as they 
should be called in this case) to show this resiliency or the endur- 
ance of paper tmder the repeated application of load, a load was 
taken in each case 10 per cent below the breaking point. This, of 
course, necessitated finding the tensile strength or breaking point 
for each grade of bag paper in both machine and cross direction. 
In order to do this an average of 10 tensile-strength tests was ob- 
tained. After obtaining in each case the desired load of 10 per 
cent below breaking point, each test sample was given this load, 
and then the load was released and the operation repeated until the 
test sample broke. All test samples for this work were cut nyi cm 
wide and long enough to allow 20 cm of paper between jaws. 
Three test samples from each grade of paper, cut in both machine 
and cross direction, were used in order to obtain an average, and 
data were collected accordingly. 



Testing Paper Bags for Cement and Lime 7 

II. EXPERIMENTAL WORK 

1. PHYSICAL AND CHEMICAL TESTS 

Each sample of bag paper was given the ordinary physical and 
chemical tests, such as weight in pounds of the standard size 
ream 25X40 — 500, bursting strength in points, tensile strength 
in kilograms, stretch in centimeters, folding endurance in number 
of double folds, fiber composition in per cent, per cent of ash, 
and per cent of rosin sizing. From these tests the ratio in per 
cent of bursting strength to weight in pounds of the standard size 
ream, 25 X 40 — 500, and the breaking length in yards were obtained 
as the best means for comparing papers of the same grade. An 
explanation and description of this ratio and breaking length 
may be procured from Circular of the Bureau of Standards No. 107. 
The results of these tests are compiled in Tables 1,2, and 4. In 
addition to the above tests the paper and bags were given the 
following special physical tests: The paper was tested for tensile 
strength in grams when it was wet, and was tested also for resili- 
ency or endurance. The numerical results are shown in Tables 
2, 3, and 4 and are presented graphically in Figs. '1 to 54. The 
bags were tested for breaking strength by determining the number 
of times each bag could be dropped before failure, as shown in Table 
5, and for strength of adhesive by determining the length of time 
each bag could be jolted before failure, as shown in Table 6. The 
purposes of these special tests were the following: The wet tensile- 
strength test was made in order to indicate what the strength of 
the paper of the bags would be when they became wet in shipment. 
The stress-strain or resiliency test was made in order to obtain a 
series of loops for each test sample, giving first the stretch at 
applied load, second the stretch when load was released, third 
the increase in stretch for every time load was applied over the 
previous time, and fourth the number of times the paper could 
stand the strain of this load before it broke. The purpose of the 
drop test was to reproduce service conditions, because a bag is 
often dropped while being handled. On the other hand, the 
jolter test not only tested the strength of the adhesive used in 
the bags but also somewhat duplicated the treatment that a bag 
undergoes while being jolted and jarred in shipment from manu- 
facturer to consumer. The following data were collected accord- 
ingly from all the above tests, and from these data it was not 
hard, by process of elimination, to choose the live bag papers 
which showed the best bursting strength, tensile strength, stretch, 



8 Technologic Papers of the Bureau of Standards 

folding endurance and resiliency, and which as bags showed the 
best breaking strength and possessed the strongest adhesive. At 
a glance, bag papers numbered 14373, 14374, 14378, 14379, an d 
1 43 8 1 seem to be the strongest. In comparing the following 
results of the resiliency test with those results of the drop test, it 
will be noted that the above papers proved strongest in both 
cases. This proves that the resiliency test is a very good test 
for showing what the paper of a bag will do in actual service, and 
since it is strictly a laboratory test, it is highly to be recommended . 

2. TABLES OF RESULTS 

TABLE 1. — Results of Ordinary Physical and Chemical Tests on Cement and Lime 

Bag Paper 



Bag-paper 

identification 

numbers 



Weight 

of the 

standard 

size ream 

25X40-500 



Bursting 
strength 
in points 



Ratio of 
bursting 
strength 
to weight 

of the 
standard 
size ream 
25X40-500 



Percentage fiber composition 



Ash 



Rosin 
sizing 



14373 
14374 
14375 
14376 
14377 

14378 
14379 
14380 
14381 



Pounds 
150 
119 
143 
127 
115 

176 
142 
172 
181 



134.0 
100.0 
108.0 
96.0 
78.0 

132.0 
143.0 
159.0 
155.0 



Per cent 
89.3 
84.0 
75.6 
75.6 
67.8 

75.0 
107.0 
92.4 
85.7 



100 jute and manila 

do 

95 jute and manila, 5 chemical wood. . . 

100 chemical wood 

100 jute and manila 

50 jute and manila, 50 chemical wood. . 
75 jute and manila, 25 chemical wood. . 

100 chemical wood 

do 



Per cent 
4.10 
3.60 
4.70 
3.30 
4.60 

2.30 

2.00 

1.27 

.97 



Per cent 
3.40 
3.80 
4.90 
3.30 
4.10 

4.40 

3.90 
.97 
1.35 



TABLE 2.— Results of Tensile-Strength Tests and Stress-Strain or Resiliency Tests 
on Cement and Lims Bag Paper 



Bag-paper 
identifica- 
tion num- 
bers 


Weight 
of the 
stand- 
ard size 
ream 
25X40— 
500 


Load at 
breaking point 


Stretch at 
breaking point 


Breaking 
length 


Load 10 per 

cent below 

breaking point 


Number of 

times load is 

applied 


Ma- 
chine 
direc- 
tion 


Cross 
direc- 
tion 


Ma- 
chine 
direc- 
tion 


Cross 
direc- 
tion 


Ma- 
chine 
direc- 
tion 


Cross 
direc- 
tion 


Ma- 
chine 
direc- 
tion 


Cross 
direc- 
tion 


Ma- 
chine 
direc- 
tion 


Cross 
direc- 
tion 


14373 

14374 

14375 

14376 

14377 

14378 

14379 

14380 

14381 


Pounds 
150 
119 
143 
127 
115 

176 
142 
172 

181 


kg 

35.0 

28.0 

27.0 

26.5 

21.5 

46.5 
37.5 
43.4 
42.3 


kg 
17.5 
16.5 
11.0 
13.0 
8.8 

18.0 
17.5 
16.4 
18.4 


cm 

0.57 
.64 
.49 
.60 
.30 

.54 
.64 
.45 
.50 


cm 

1.57 
1.60 
1.25 
1.43 
.70 

1.34 
1.06 
1.12 
1.14 


Yards 
7130 
7160 
5770 
6380 
5710 

5100 
8060 
7730 
7160 


Yards 

3565 
4240 
2350 
3140 
2340 

3120 
3770 
2910 
3110 


kg 

31. 5Q 
25.20 
24.30 
23.85 
19.35 

41.85 
33.75 
39.06 
38.07 


kg 

15.75 
14.85 

9.90 
11.70 

7.92 

16.20 
15.75 
14.76 
16.56 


5.66 
21.66 
30.30 
26.00 
11.00 

49.66 

12.00 

1.00 

59.00 


8. '66 
12.33 
19.33 

8.66 
11.66 

4.66 
9.66 
2.00 
9.66 



Testing Paper Bags for Cement and Lime 



TABLE 3. — Results of Stress-Strain or Resiliency Tests on Cement and Lime Bag 
Paper, Showing Different Stretches 





Loop 

1 


Loop 
3 


Loop 

5 


Loop 

10 


Loop 
20 


Loop 

30 


Loop 

40 


Loop 

60 


Bag identification No. 14373: 
Stretch at applied load — 


do 


1.68 
5.66 

.25 
.90 

2.60 
6.28 

.30 
.94 

1.18 
3.85 

.27 
.53 

1.75 
5.23 

.31 
.80 

1.16 
2.90 

.23 
.40 

1.68 

5.46 

.26 
.82 

2.31 
4.93 

.38 

.80 

2.10 
3.13 


2.01 
5.77 

.36 
.91 


2.30 

.40 
1.03 














6.10 










Stretch when load Is released — 


do.... 

do 

do.... 












1.05 

2.65 
7.80 

.47 
1.44 

1.90 










Bag identification No. 14374: 
Stretch at applied load — 


2.75 




2.95 


3.15 




6.96 
1.27 

5.13 
.86 

5.90 

.38 
.99 

3.75 
.67 


7.56 

.42 
1.34 

1.56 




Stretch when load is released — 


.51 




.54 


.56 


Bag identification No. 14375: 
Stretch at applied load — 


do.... 

..centimeters.. 
do.... 

do.... 

do.... 

percent.. 


2.22 
5.40 

.50 
.92 

2.75 
6.60 

.60 


2.60 








5.60 




Stretch when load is released— 


.36 


.44 








1.00 




Bag identification No. 14376: 
Stretch at applied load — 


2.16 
6.50 

.44 

1.65 
.36 


2.51 

.51 
1.02 

2.00 
4.05 

.43 

.70 

1.90 












Stretch when load is released — 
















Bag identification No. 14377: 
Stretch at applied load- 












4.30 








Stretch when load is released — 


centimeters.. 
do.... 

do.... 










.75 








Bag identification No. 14378: 
Stretch at applied load- 










6.38 
1.06 

5.28 

.50 
.95 


7.12 

.32 
1.20 

2.55 
5.45 

.58 
1.00 










Stretch when load is released — 


.40 




















Bag identification No. 14379: 
Stretch at applied load — 


do.... 

do.... 


2.85 
5.60 

.64 
1.05 


3.10 
6.00 

.70 
















Stretch when load is released— 
















Bag identification No. 14380: 
Stretch at applied load- 












3.60 














Stretch when load is released — 
















do.... 

do 


.50 

1.53 
3.13 

.32 

.44 


.78 

3.90 
.56 














Bag identification No. 14381: 
Stretch at applied load- 


1.83 
4.50 

.42 
.66 


2.10 
4.95 

.49 
.72 


2.33 
















Stretch when load is released — 


do.... 


.54 


























33325°— 21 2 





















IO 



Technologic Papers of the Bureau of Standards 



TABLE 4.— Results of Wet Tensile Tests and Folding Endurance Tests on Cement 

and Lime Bag Paper 



Bag-paper Identification numbers 


Wet tensile 
strength 


Breaking length 


Folding endurance 

in number of double 

folds 




Machine 
direction 


Cross 
direction 


Machine Cross 
direction direction 


Machine 
direction 


Cross 
direction 


14373 


kg 
1.38 
2.36 
1.43 
2.05 
1.17 

3.15 

1.31 

.80 

1.26 


kg 
1.40 
1.71 
1.29 
1.68 
.92 

1.35 

.71 
.30 
.69 


Yards 

476 
1026 
519 
836 
525 

926 
349 
243 
362 


Yards 

482 
746 
468 
685 
418 

396 

262 
90 
199 


10 000+ 
10 000+ 
10 000+ 

6 220 
10 000+ 

10 000+ 
10 000+ 

7 244 
10 000+ 


10 000+ 


14374 


10 000+ 


14375 


1 998 


14376 


4 260 


14377 


5 011 


14378 


10 000+ 


14379 


10 000+ 




10 000+ 




10 000+ 







TABLE 5. — Results of Drop Service Tests on Cement and Lime Bag Paper 



Bag-paper 

identification 

numbers 


Position of bag when 
dropped 


Number 
of drops 
before 
failure 


Extent of failure 




On side and seam up 

do 


2 
3 
1 

1 
1 

4 
4 
1 

3 


Paper failed at seam. 
Do. 


14374 


14375 


do 


Paper and glue failed at seam. 
Paper failed across edge, and glue failed at end. 
Paper and glue failed at seam, and paper failed 
across bottom side. 

Paper failed at seam. 
Do. 


14376 


do 


14377 


do 


14378 


do 


14379 


do 


14380 


do 




14381 


.. do 


failed at end. 









TABLE 6. — Results of Jolter Service Tests on Cement and Lime Bag Paper 



Bag-paper identification numbers 


Position of bag when 
jolted 


Minutes 
jolted 
before 
failure 


Extent of failure 


14373 


On side and seam up 

do 


24 
60 

1 
18 

6 

40 

30 

2 

3 




14374 . 




14375 ... 


do 




14376 


do 


Do. 


14377 


do 


Do. 


14378 


do 


Do. 


14379 . . 


.. ..do 


Do. 


14380 


.. ..do 


Do. 


14381 


do 


Do. 









Testing Paper Bags for Cement and Lime 



II 



3. DIAGRAMS ILLUSTRATING RESULTS 




toopflt 



FlGS. i to 6. — Diagrams showing resiliency or endurance of cement and lime bag paper 
in ike machine and cross directions 



12 



Technologic Papers of the Bureau of Standards 




Figs. 7 to 14. — Diagrams showing resiliency or endurance of cement and lime bag paper 
in the machine and cross directions 



Testing Paper Bags for Cement and Lime 



13 




F13. 31 



BpocIdob Dimensions: 

3 1/3 X 30 CenUao&ssa, 



FlGS. 13 to 22. — Diagrams 



showing resiliency or endurance of cement and lime bag paper 
In the machine and cross directions 



14 



Technologic Papers of the Bureau of Standards 




Figs. 23 to 30. — Diagrams showing resiliency or endurance of cement and lime bag paper 
in Hie machine and cross directions 



Testing Paper Bags for Cement and Lime 



15 




pig. 37 



Halt: 14379 - Maohl-OT 



SpeolQQD Dimeiioicne: 

2 1/3 X SO oentimsserp 



loops 1.1 - 5 - 6 — 10 - 39 



FIGS. 31 to 38.— Diagrams showing resiliency or endurance of cement and lime bag pape 
in the machine and cross directions 



i6 



Technologic Papers of the Bureau of Standards 




Mark: 14330 - MftoMno.^-tl^ 

BpoolEan Dlaanelons: 

.3 1/3 K 20 Caatlaotar* 



Figs. 39 to 46. — Diagrams showing resiliency or endurance of cement and lime bag pape 
in the machine and cross directions 



Testing Paper Bags for Cement anal Lime 



17 




Figs. 47 to 54.— Diagrams showing resiliency or endurance of cement and. lime 
in the machine and cross directions 



1 8 Technologic Papers of the Bureau of Standards 

III. CONCLUSIONS 

Conclusions to be drawn from the above results of tests, taking 
into special consideration the various tests on the chosen five best 
bags, are that a satisfactory cement or lime bag paper should 
have a very good bursting strength and a high tensile strength 
and stretch in both directions. It must also have a high endurance 
or resiliency, which is determined by the simple drop service test 
or by the better stress-strain laboratory test. A suitable bag 
paper must also show a good tensile strength when wet and must 
have a high folding endurance. As the above data show, it is 
not necessary to manufacture a bag out of very heavy paper in 
order to obtain a bag of the very best quality. For instance, bag 
paper numbered 14374 weighs only 119 pounds to the standard 
size ream 25X40 — 500, and yet is one of the five best papers 
tested. The fiber composition of a good bag paper should be not 
less than 50 per cent strong manila and jute and the remainder 
chemical wood. The ash should not be over 3 per cent and the 
rosin sizing should be at least 3.5 per cent. 

IV. SPECIFICATION 

In writing up the specification for cement and lime paper bags 
it does not seem wise to recommend any specific weight of paper, 
since this study shows that weight alone should not be considered 
in choosing the best-quality bags. It is for the consumer to 
decide what weight bag he wishes to use and for the manufacturer 
to decide what weight bag paper he wishes to manufacture. 
However, it is thought that both manufacturer and consumer 
would prefer a light-weight paper for reasons of economy. For 
these reasons weight is not given in the following specification, 
but in all other respects it is thought that this specification will 
meet au requirements and can be adhered to by the manufacurers 
without any difficulty, and that bags made of paper that conforms 
to this specification will prove satisfactory to the cement and lime 
manufacturers . 

SPECIFICATIONS FOR PAPER BAGS FOR CEMENT AND LIME 

Bursting strength: Not less than 100 points. 

Ratio bursting strength to weight in pounds of the standard- 
size ream, 25 X40 — 500: Not less than 75 per cent. 

Fiber composition: Not less than 50 per cent manila and jute; 
the remainder as chemical wood. 



Testing Paper Bags for Cement and Lime 19 

Ash: Not over 3 per cent. 

Rosin: Not less than 3.5 per cent. 

Tensile strength (test sample 2% cm wide and 20 cm between 
jaws): Not less than 28 kg (machine direction), 16 kg (cross 
direction) . 

Breaking length : Not less than 7000 yards (machine direction) , 
3500 yards (cross direction). 

Wet tensile strength (test sample 15 mm wide and 90 mm be- 
tween jaws): Not less than 2000 g (machine direction), 1300 g 
(cross direction) . 

Wet breaking length: Not less than 800 yards (machine direc- 
tion), 400 yards (cross direction). 

Folding endurance (test sample 15 mm wide and 90 mm be- 
tween jaws): Not less than 10 000 double folds (machine direc- 
tion), 10 000 double folds (cross direction). 

Resiliency strength (test sample 2% cm wide and 20 cm be- 
tween jaws): Not less than 20 times (machine direction), 9 times 
(cross direction) . 

Breaking strength of bags: Not less than 3 times. 

Adhesive strength: Not less than 30 minutes. 

Washington, September 20, 1920. 




LIBRARY OF CONGRESS 

015 992 289 3 




